Steel piston ring

Abstract

In a corner portion ( 2 ) defined between an outer peripheral surface ( 4 ) and a lower-side surface ( 3 ) of a steel piston ring ( 1 ), a groove ( 5, 6 ) having either an approximately quadrangular shape with a length of one side of 0.05 to 0.4 mm or an approximately quarter circular shape having a radius of 0.05 to 0.4 mm is formed. A sharp edge ( 9 ) formed by the groove ( 5, 6 ) performs an oil scraping function and the groove ( 5, 6 ) works to reduce an oil pressure of a second land or a third land clearance between the cylinder bore and the piston.

1 . A steel piston ring for an internal combustion engine, characterized in that a groove having either an approximately quadrangular cross section with a length of each side of 0.05 to 0.4 mm or an approximately quarter-circular cross section with a radius of 0.05 to 0.4 mm is formed at a corner portion defined by an outer peripheral surface and a lower-side surface of the piston ring body and the groove is continuously extended to abutting end faces.  
     
     
         2 . A steel piston ring according to  claim 1 , wherein the outer peripheral sliding surface is formed in either a barrel shape or a taper shape.  
     
     
         3 . A steel piston ring according to  claim 1  or  2 , wherein the piston ring is a pressure ring.  
     
     
         4 . A combination of piston rings having a plurality of pressure rings for an internal combustion engine, characterized in that at least two piston rings thereof satisfy the constituent features of  claim 1  or  claim 2.